I understand than mainstream nutrition is incorrect and more fat in your diet generally does not mean more fat on you.

A little anecdotal evidence.

I'm 18 and like you I've never been particularly fat. I've been bulking for quite a few months now, with A LOT of fat. Smearing butter on everything, etc. Ive gained about 30 lb and put on very little fat. I went from vaguely visible abs to visible ab outline.